You are not currently logged in.
Access your personal account or get JSTOR access through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Evolution of Variation and Distributional Patterns in European Populations of the Three-Spined Stickleback, Gasterosteus aculeatus
Vol. 17, No. 3 (Sep., 1963), pp. 320-332
Published by: Society for the Study of Evolution
Stable URL: http://www.jstor.org/stable/2406161
Page Count: 13
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
Variation in the bony armature in the European three-spined stickleback (Gasterosteus aculeatus) shows obvious geographical relationships. The bases of the distributional pattern of the types, trachurus, semiarmatus, and leiurus, are the different ecological requirements of these three types of armature. Well-defined genotypes underlie the corresponding phenotypes. There may be distinguished: (1) Pure trachurus populations in coastal waters of northern Europe, in parts of the Baltic, and in the Black Sea. (2) Pure leiurus populations (a) in the perimediterranean fresh water of southern Europe, and (b) in fresh waters of central, northern, and northwestern Europe when isolated from the sea. (3) Mixed populations in coastal waters of northwestern Europe and in parts of the Baltic. In such populations the three types of armature are represented in different percentages, which are related to geographical latitude. The semiarmatus type occurring in these populations must be regarded as a hybrid between trachurus and leiurus. However, in certain lakes in Romania and Turkey, semiarmatus-like individuals are not hybrids for they occur either as one extreme of variation or as the only form present. The modern distributional pattern of the species with its different types of armature is interpreted on the basis of the zoogeographical effects of the last glaciation. The recent distributional pattern is the result of a postglacial spreading, in which the different types of armature participated according to their respective ecological requirements; it is furthermore the result of hybridization and selection, which the three types underwent in different degrees both within the marine and freshwater populations.
Evolution © 1963 Society for the Study of Evolution